Enrollment opens Nov. 1 and runs through Dec. 15 for individual health insurance plans subsidized through the Affordable Care Act. Although it is under fire from some politically conservative sectors, about 79,400 Mainers are covered through this insurance program. Help is available from many sources, including the official website, www.healthcare.gov.

Bob Farnsworth, a self-employed builder in Machias, knows the future of the Affordable Care Act is profoundly uncertain. But the embattled health reform law has provided the first affordable health coverage of his adult life, and he was enthusiastically prepared for the sign-up period for this year that kicked off Wednesday.

“Once you’re in the system, you’re able to think in terms of actually getting health care,” the 61-year-old said. “Without it, I would never have even considered getting a colonoscopy, for example. I’ve also gotten the physical therapy I needed and some cardiology care.”

Before the ACA, “anecdotally, I would hear people say they were paying $1,000 a month or $750 a month or something like that,” he said. “None of those numbers were ever going to work for me.”

But with the ACA, also called Obamacare, Farnsworth pays just $130 per month for his plan, with a subsidy of close to $800 that covers the balance. He’s still responsible for an annual deductible of about $2,500, and he pays tax on the value of the subsidy.

Despite the current political climate, the insurance marketplace and its subsidies remain the law of the land. Potential changes at the federal level, including a hot-button debate about repealing the ACA altogether, are unlikely to take effect in 2018, experts say. Most expect no disruption of the system of income-based premium discounts, mandated health benefits and other elements that have made meaningful health insurance affordable for some 78,400 Mainers since the program went live in 2014.

With the premium discounts, which are based on income, many plans will cost Mainers less than last year. Some of the most basic plans will even carry zero dollar monthly premiums after the discounts for consumers with low incomes.

But many residents may not realize that. Against a steady, high-decibel drumbeat of political opposition, President Donald Trump’s administration shortened the program’s open enrollment period, curtailed operations at the official website HealthCare.Gov, cut the budget for advertising and consumer education, and eliminated funding for a provision that reduces out-of-pocket spending for lowest-income enrollees.

“Until Washington decides what it’s going to do, it’s very hard for insurers and consumers to do any long-term planning,” Maine’s insurance superintendent Eric Cioppa said.

That’s no reason for Mainers to stay away from ACA plans for the coming year, he said.

“Where else are you going to find a subsidy?” he asked.

Obamacare provides private insurance options for Americans who don’t have health coverage through their employers and who don’t qualify for Medicaid or other government programs.

People already enrolled in one of those plans, and those interested in enrolling for the first time, have until Dec. 15 to choose.

The signup period this year is about six weeks, considerably shorter than in previous years.

ACA marketplace plans are tiered as bronze, silver or gold, reflecting their premium cost, out-of-pocket spending requirements and the value of the benefits they provide. Though monthly premiums are slated to rise steeply for 2018 — as much as 35 percent in the popular silver-level plans — Cioppa and other experts emphasize that those increases will be offset for many enrollees by more generous subsidies.

In many areas of the country, including Maine, the average cost of gold and bronze plans will be lower in 2018 than last year, after the subsidies, according to a recent analysis by the Kaiser Family Foundation.

Premium subsidies are more generous for low-income households and less generous for higher-income households. Households earning up to 400 percent of the federal poverty level — that’s $98,400 for a family of four — can qualify for a subsidy.

According to a rate calculator on the Maine Bureau of Insurance website, a silver plan from Community Health Options for a single, 42-year-old, non-smoking male in Cumberland County carries a monthly premium of $621.03. But with a household income of $24,000, a spokesman said the federal subsidy would bring the cost down to about $220 per month.

Similar plans are available through Harvard Pilgrim Health Care, the only other insurer participating in the marketplace in Maine. Anthem announced in September that it would retreat from Maine’s ACA market. Mainers already enrolled in an Anthem marketplace plan can stay with Anthem in an off-marketplace plan with no subsidy or shop for a new plan with one of Maine’s other two marketplace carriers. Those who don’t make a choice will automatically be assigned to another marketplace plan.

In addition to general public uncertainty about Obamacare’s future, Trump’s recent defunding of one provision for lowest-income enrollees — the so-called “cost-sharing reduction” — has caused widespread but unnecessary concern, said Kate Ende of the advocacy group Maine Consumers for Affordable Health Care.

The cost-sharing reduction is separate from the tax credits that reduce monthly premiums. It instead reduces co-pays, deductibles and other out-of-pocket spending for lower-income enrollees, those earning up to 250 percent of the federal poverty level. While the federal government will no longer reimburse insurers for the cost-sharing reduction payments, insurers are still on the hook to provide it to policyholders. So as lawmakers explore alternate funding solutions, Ende said, low-income enrollees can still expect to receive the financial help.

“People are concerned that the marketplace will shut down or that they won’t qualify for a subsidy,” Ende said, but Mainers who shop around are likely to find an affordable plan.